In a machine, such as a wheel loader or a track type tractor, for example, an engine supplies power for propelling the machine in the forward or reverse directions as well as supply power for machine implements. A transmission is coupled to the engine and transmits power from the engine to the drive train to propel the machine. It is desirable to utilize a continuously variable transmission and manage the transmission ratio to hereby save engine power for the implements and also to provide a continuously variable power flow through the transmission to improve machine productivity. Because machines operate at relatively low speeds and in cyclical work routines, there is a need to control speed precisely and to be infinitely adjustable throughout the full range of the transmission. One of the problems associated with such an arrangement is to provide an electro-mechanical transmission that will operate at high efficiencies over a wide variety of operating conditions.
The present invention is directed to overcoming one or more of the problems as set forth above.